The present invention relates to a process for removing particles of paint overspray from an aqueous turbid liquid, the particles of paint overspray being present in floating and dispersed form, as well as in submerged and coagulated form, at least the dispersed and submerged particles of paint overspray forming sediment and then being removed. In addition, the present invention relates to an apparatus for carrying out this process, this having at least one sedimentation tank.
Particles of paint overspray are washed out wet and move into sedimentation-removal plants. DE 93 04 854 U1 describes an apparatus for separating paint sludge and water for a paint-mist separator plant. In this, the sediment in a quiescent turbid liquid settles on the bottom of the tank, whereas the floating particles remain on the surface of said turbid liquid. The floating particles are removed by a conveyor with a skimmer. The paint sludge that builds up is removed from the bottom of the container through a sump that can be shut off, using delivery pumps, and the turbid water that has been cleansed is drained off. One disadvantage of this is that when the sediment is being removed or when the floating particles are being skimped off the surface of the turbid liquid, if the paint has not fully dried, this leads to agglomeration of the paint particles and hardening, and thus to blockages and excessive loads on the motors used for the loader and the pumps. In addition, if the feed line is left open, the tank can flood, so the level to which the tank is filled must be monitored constantly, either manually or by a level sensor.
DE 39 23 437 A1 describes a painting process and apparatus, in which the sediment is flushed out of a first tank into a second tank through a line that connects the two tanks, and is then concentrated in the second tank. Once again, it is a disadvantage that the mixture composed of water and tacky paint particles must pass through components such as filters, nozzles, and pumps that are easily blocked, so that once again this can result in agglomeration and adhesion and thus to the failure of such components. In addition, the sediment can only be removed from the sump at the bottom of the second tank by means of a collector basket. The collector basket can only be removed and cleaned manually, when the plant is not operating, so that economic disadvantages result from this fact alone.
DE 38 37 638 A1 describes how the surface level of the turbid liquid within the tank can be raised by causing it to build up by means of a movable sliding dam and then decanting a floating layer composed of greases, highly viscous oils and other floating substances by way of an overflow edge. Because of the required parts of the movable sliding dam, which are exposed to the turbid liquid, this process is not suitable for separating tacky paint particles since there is always a possibility that the mechanical guides for the sliding dam may gum up. Particles that do not float but which form sediment thus cannot be removed by this.